As a conventional electron multiplier, an electron multiplier including a micro-channel plate (hereinafter also referred to as an “MCP”) formed by forming a number of fine through-holes (channels) in a thin plate-shaped glass substrate is known. In this electron multiplier, when the electrons are incident on a channel of the micro-channel plate to which a voltage has been applied, the electrons repeatedly collide with a sidewall in the channel and secondary electrons are emitted such that the electrons are multiplied, and the multiplied electrons are detected in an anode. As such an electron multiplier, an electron multiplier in which a dielectric insulator is film-deposited on a micro-channel plate is disclosed, for example, in Patent Literature 1.